Electric Motor

ABSTRACT

An electric motor for conveying media includes (a) a stator; (b) a rotor including a rotor magnet; and (c) a media throughput opening between the stator and the rotor. A smallest inner diameter of the stator is 1.5- to 8-times as large as a largest outer diameter of the rotor magnet.

FIELD OF INVENTION

The present invention relates to an electric motor.

BACKGROUND INFORMATION

Electric motors are known in various embodiments. For example, motorsare known for conducting media, which comprise a rotor and a statorlocated around this, wherein the rotor is connected to a media impellerand by way of this may regulate the flow of media.

With motors leading media, one strives for a simple construction as wellas highest possible integration into an existing housing system. Here,apart from observing the desired simplicity for reasons of repair, oneshould also take note of the sealedness, in particular with regard tothe electrical conducting parts of the electric motor.

SUMMARY OF INVENTION

The present invention relates to an electric motor which has anextremely simple construction, has a good sealedness with regard to themedia to be delivered and despite this has a high performance and isenergy efficient.

Here, it is the case of an electric motor for delivering media, whereinthis comprises a stator, a rotor with a rotor magnet, as well as a mediapassage opening between the stator and rotor. Here, the smaller innerdiameter of the stator is 1.5- to 8-times, preferably 2- to 4-times thatof the largest outer diameter of the rotor magnet.

Here, basically all substances capable of flowing are to be understoodas “media”, e.g. gases, liquids, pastes, dusts or granular substances.

The “largest outer diameter” of the rotor magnet is to be understood asthe diameter which the actual magnetically effective material actuallyhas (this without sheathing around the rotor magnet). If the rotormagnet does not have a circularly round shape, then the largest outerdiameter is to be understood as the largest possible inscribed circle inthe respective cross section of the magnet material

The “smallest inner diameter of the stator” is to be understood as thesmallest diameter of the electrically or magnetically actually effectivestator. A shielding e.g. of a plastic material from the stator towardsthe rotor, which for example serves for corrosion protection, with thisis not to be seen as part of the stator, but only the smallest diameterof the (as a rule metallic) electrically or magnetically effective partscount. With regard to the motor according to the invention, it is thecase of a media gap motor, thus of a permanent magnet synchronous motorwith the particular characteristic of an excessively large air gapbetween the stator and the rotor. This large air gap permits thetransport of various media between the rotor and the stator in the axialdirection. The rotor magnet here may be directly coupled to a deliverydevice or also integrated into this.

With conventional air gap motors, the smallest possible constructionalsize for the desired torque as well as a high magnetic flux with alowest application of permanent magnetic material is desired, with aconventional design of the motor without the use of media/throughputfunction of the air gap. Thus with conventional motors, one thusobserves a small air gap on account of the fact that the magneticresistance in the air gap is larger than in the ferromagnetic part ofthe magnetic circuit.

The present media gap motor is basically constructed as a conventionalpermanent magnet synchronous motor, but with the particularity of astator inner diameter which is overdimesionally large compared to theouter diameter of the rotor of the permanent magnet.

In order to produce the required magnetic flux despite the large gapbetween the rotor and the stator, and the high magnetic resistance whichthis entails, as well as the high scatter share at the pole transitions,it requires the application of magnets which have a very high remanenceand a very high energy density. In particular, rare-earth magnetmaterials are suitable for this. The magnet height simultaneously needsto be adapted accordingly. A high motor efficiency with respect to thediameter of the rotor or magnet may be achieved despite the relativelylow flux, since a relatively large winding area is available due to thelarge outer diameter of the stator.

It is particularly amazing for the man skilled in the art, that one maydesign a well functioning motor despite the unusually large air gap.

Here, the large gap between the rotor and stator even permits to rotormagnet to be displaced somewhat in the axial direction (direction of therotation axis) without the characteristic values noticeably worsening byway of this.

The rotor of the electric motor preferably has a rotor magnet which issurrounded by a sheathing. The rotor magnet is mechanically protected byway of this. One may also have an influence on the type of magneticfield in this manner. The rotor magnet may be designed such that it ispartly or completely integrated into the compressor wheel. If thecompressor wheel consists of fibre-reinforced or non-reinforced plastic,then on production, the rotor magnet may be directly peripherallyinjected with the plastic mass, by which means an inexpensivelarge-scale manufacture is possible.

The electric motor preferably contains a stator which has an essentiallyhollow-cylindrical shape and which surrounds the rotor in a concentricmanner. Here, it is advantageous that the stator may be designed as partof the inner wall of the compressor housing. The stator may for examplealso be applied as an insert into a corresponding opening of thecompressor housing. The advantage with these embodiments is the factthat only an as small as possible design change of conventionalmechanical turbochargers is necessary, so that cost- and competitiveadvantages may be realised by way of this, in particular withlarge-scale production.

Apart from the variants mentioned above which focus on the outersurrounding of the stator, the stator may yet also be provided with ashielding towards the rotor. This serves for the protection of thestator, in particular for corrosion protection. The shielding maypreferably be given in the form of a thin tube or flexible tubing,wherein this shielding is preferably designed of electrically andmagnetically not-conductive material.

Thus as a whole, the hollow-cylindrical design of the stator isadvantageous but not absolutely necessary.

The rotor may be designed in different manners. The motor preferably hasa rotor shaft, wherein this rotor shaft is mounted in a simple or in amultiple manner over its length. In a particularly advantageousembodiment, the rotor shaft is essentially mounted on one side andprojects out essentially freely on the other side. Thus the necessity ofa further bearing location and, as the case may be, struts between therotor and stator which could further increase the throughput resistance,may be done away with. A further embodiment envisages the rotor magnetin the inside being hollow in regions, for placing on a common shaftconnected to a medium impeller or a medium conveyor worm. An even betterintegration of the rotor shaft or the drive shaft with the rotor magnetand even a part delivering medium (medium impeller medium conveyor worm)may be effected in this manner. It is advantageous on integrating therotor magnet into the rotor shaft or the medium impeller/medium deliveryworm, for the components adjacent to the rotor magnet to be of amaterial which is not magnetically conductive or very poorlymagnetically conductive, preferably of reinforced or non-reinforcedplastic.

A further advantages formation envisages the mounting of the rotor shaftbeing non-lubricated or being lubricated by the medium to be delivereditself (this is advantageous for example with hydrodynamic bearings). Asa whole practically any media may be considered for the delivery withthe electric motor according to the invention, specifically all gases(in particular air) as well as liquid media (in particular aqueousmedia).

One particular advantage of the medium gap motor according to theinvention lies in the fact that the axial centre of the stator and theaxial centre of the rotor may be displaced in the axial direction, andspecifically by tenth up to a fifth of the largest axial extension ofthe rotor magnet. The electric motor according to the invention isparticularly suitable for the use in an electrically supportedturbocharger with a freely projecting electric motor, for the transportof explosive gases, dusts, vapours, sticking substances, pastes, liquidssuch as water or oil; decomposing products, such as foodstuffs; inventilation devices, in pumps, in particular in pumps for aggressivemedia, such as salt water, chemical solutions (in particular in theorthodontic field); in disinfectable or sterilisable pumps, canned pumps(medium transport in the axial direction), metering pumps, micro-pumps,disposable pumps, multi-stage pump systems; for use in turbines,generators, delivery worms for example for granular media, fluids orpastes; in gas-, water- and steam turbines; in devices for measuring themedia flow via a generator voltage.

BRIEF DESCRIPTION OF DRAWINGS

The present invention is now explained by way of several figures. Thereare shown in

FIGS. 1 a to 1 d show views of a turbocharger, with which the electricmotor according to an exemplary embodiment of the present invention isapplied,

FIGS. 2 a and 2 b show cross-sectional views of an electric motoraccording to the present invention,

FIGS. 3 to 6 show views or sections of further exemplary embodiments ofthe electric motor according to the present invention.

DETAILED DESCRIPTION

One application example of the invention is firstly shown by way of theFIGS. 1 a to 1 d.

FIGS. 1 a to 1 d show a turbocharger 1 which may be coupled to a turbinehousing 5 on an internal combustion engine. After the combustion, theexhaust gas is collected by way of the exhaust gas fans shown in FIG. 1a and is used for driving a turbine wheel 2. The turbine wheel 2 issurrounded by the turbine housing 5 and is essentially deduced from aconventional mechanical turbocharger. A bearing housing 7 connects tothe turbine housing 5, and then a compressor housing 6. A compressorwheel 6 is attached in this compressor housing 6, and compresses the airfed through an inlet opening (this inlet opening is in particular easilyseen in FIG. 1 c) and leads it to the combustion space of the internalcombustion engine in a manner which is not shown here. The compressorwheel 3 on the left side in FIG. 1 a shows a continuation, to which arotor 4 a of an electric motor is given. The rotor 4 a is attachedcentrally in the inlet air opening 4 e.

A stator 4 b which has an essentially hollow-cylindrical shape and isrepresented as part of the inner wall of the compressor housing in theregion of the inlet air opening, is provided around the rotor 4 a. Here,the stator 4 b is even provided as an insert into a suitable opening, sothat this may be assembled very easily. Here therefore in FIG. 1 a, therotor gap between the rotor 4 a and the stator 4 b is the inlet airopening 4 e for the compressor wheel. With this, the inlet air opening 4e is free of struts between the rotor and the stator also according toFIG. 1 a. The smallest inner diameter of the stator (see “d_(s)” in FIG.1 d) is 1.5 times larger than the largest outer diameter d_(R) of therotor.

The rotor 4 a of the electric motor 4 comprises a rotor magnet 4 c whichhere is surrounded by an sheathing (see e.g. FIG. 1 d). With this, thesheathing is designed in an essentially “beaker-shaped” manner, whereinthe base of the beaker is almost completely closed towards thecompressor wheel (disregarding a centric assembly bore).

The compressor wheel may (but need not) be of a non-metallic material,here with one embodiment, for example of a non-reinforced plastic, andthe influence on the electromagnetic field of the electric motor isminimised. The rotor magnet 4 c in turn is hollow in regions for placingon a common shaft with the compressor wheel. Here, a bore 4 c of therotor magnet is to be accordingly seen in FIG. 1 d. Furthermore, it maybe seen that a sequence of elements is shown in the sequence of therotor (consisting of the rotor magnet 4 c and sheathing 4 d), thecompressor wheel 3, shaft 8, turbine wheel 2, which minimises a thermalloading of the electric motor. The shaft 8 here in the presentembodiment is designed such that the turbine wheel 2, compressor wheel 3as well as rotor 4 a are firmly (rotationally fixedly) connected to oneanother, thus may not be separated by a rotation clutch or free-wheel.

However, it is basically possible to provide such a clutch within theframework of the present invention, if it is the case for example thatthe turbine wheel 2 is very high, but however the design effort would inturn also be increased by way of this.

The nominal voltage of the electric motor 4 in FIG. 1 a here is 12 V,but other voltages (for example 48V for hybrid vehicles) are alsopossible.

The electric motor may be operated in motor operation (for acceleratingand avoiding a “turbolag”), as well as in generator operation (forrecovering energy). If the charging pressure (in the turbine housing)reaches a certain nominal value, then additional energy is produced byway of using a converter capable of return feed. Ideally, one may doaway with a wastegate/pressure dose for blowing out excess exhaust gaspressure, as is represented in FIG. 1 b, numeral 9, by way of thisenergetic conversion of the braking energy in generator operation.

The turbocharger according to the invention is used in a drive systemaccording to the invention for motor vehicles which contain an internalcombustion engine connected to the turbocharger, as well as a storagedevice for electrical energy. The electric motor of the turbocharger 1here is connected to the storage device for electric energy for takingelectrical energy in a motor operation of the turbocharger 1, and forfeeding in electrical energy in a generator operation of theturbocharger. In a particularly preferred embodiment, the electric motorof the turbocharger is connected to an electrical storage device,wherein this electrical storage device is additionally connectable to anelectromotoric drive of a motor vehicle. This may be a “hub motor” of amotor vehicle or another electric motor, which is provided in the drivetrain of a motor vehicle (for example in the region of the gear). Thisconnection of the electrical turbocharger to a hybrid vehicle isparticularly energy efficient.

Control electronics for determining the rotational speed of the turbinewheel 2 or the compressor wheel 3, actual values of pressure conditionson the turbine housing side and compressor housing side, as well asfurther values relevant to the torque for the internal combustion engineare provided for the efficient control of the drive system or theturbocharger.

FIG. 2 a shows a field line representation of the magnetic flux betweenthe rotor 4 a and the stator 4 b.

FIG. 2 b once again shows the geometric particulars of the electricmotor according to the invention. Here one may see a solid-cylindricalrotor magnet which has a largest diameter d_(RM). A sheathing 4 d isattached around this rotor magnet 4 c. In turn, a medium impeller 10 ais attached on this sheathing. A medium passage opening 4 e is givenaround the media impeller 10 a and this is surrounded radially outwardlyby a shielding 11. The actual stator 4 b, whose outer diameter isspecified at d_(s) is then given around the shielding 11.

With the exemplary electric motor, the remanence is 1.28 Teslas, theenergy density 315 kJ/m³ and the rotor magnet consists of NdFeB.

Here then, an electric motor 4 for the delivery of media is shown,wherein this comprises a stator 4 b, a rotor 4 a with a rotor magnet 4c, as well as a media passage opening 4 e between the stator and rotor.The smallest inner diameter d_(s) of the stator, here is 1.5-times to8-times, preferably 2-times to 4-times as much as the largest outerdiameter of the rotor magnet itself (d_(RM)), in the present cased_(s)=2×d_(RM).

The rotor magnet is preferably surrounded with a sheathing for theprotection from media or damage. This may be designed in a beaker-likemanner. The stator is preferably designed as an insert into acorresponding opening of a surrounding housing. A shielding 11 ispreferably provided to the inside, thus towards the media passageopening, and this protects the stator from corrosion and improves theflux characteristics.

This is preferably designed in the shape of a tube, wherein the tube isof an electrically and magnetically non-conductive or poorly conductiveplastic e.g. glass fibres, alternatively e.g. of glass or rubber. Therotor particularly preferably has a rotor shaft, wherein this rotorshaft is mounted in a simple or multiple manner over its length. Therotor shaft here is preferably mounted on one side and thus in a“projecting” manner.

The flow resistance through the rotor is further reduced by way of this.The rotor magnet is preferably placed on a common shaft with a mediaimpeller or a media conveyor worm or is integrated in the inside andthus centered straight away. One may again attach a media impeller or amedia conveyor worm around the motor magnet (these have recesses forreceiving the rotor magnet), so that an as large as possible integrationof the components is possible.

FIG. 3 shows a use of an electric motor which comprises a media impeller10 a of a plastic material. A rotor magnet 4 c is attached on theend-side of this media impeller 10 a. Bearing locations 12 mount a rotorshaft 8 which is screwed in the medium impeller. A stator 4 b isaccommodated in an inner wall of a housing 6. The flow of a medium 13 isintroduced from the left, and is conveyed towards the right by the mediaimpeller 10 a. Preferably, in the present case, again there is a largegap width not only radially about the axis 14, but also axially in thedirection of the axis 14. This is also due to the fact that the axialcentre of the stator AZS and the axial centre of the rotor AZR aredisplaced in the axial direction, and specifically by a tenth to a fifthof the largest axial extension GAAR of the rotor magnet.

FIG. 4 shows a representation corresponding essentially to FIG. 3,wherein here a shielding 11 is additionally provided, which protects thestator from the medium 13.

FIG. 5 shows a further embodiment of a pump according to the inventionor of a throughput meter according to the invention, with which threepropellers 10 a are mounted on a rotor shaft 8. With this, the bearingsare attached on the left, as well as on the right side of the threemedia impellers 10 a. The stator 4 b is attached in the axial directionwith respect to the axis 14 centered about the rotor magnet 4 c. Themedia impellers have an inner cavity which accommodates the rotor shaft8 or the rotor magnets 4 c located therein. A particularly simple andsecurely mounted device is given in this manner, and by way of suitablewebs, on the one hand the retention of the rotor shaft 8 is ensured, andalso an adequate throughput of media 13 is achieved on account of therelatively small web cross sections.

FIG. 6 shows an embodiment example which is quite similar to FIG. 5.However, here a media conveyor worm 10 b is provided instead of thethree individual impellers 10, and this seals media towards theshielding 11 in a particularly good manner.

1. An electric motor for conveying media, comprising: a stator; a rotorincluding a rotor magnet; and a media throughput opening between thestator and the rotor, wherein a smallest inner diameter of the stator is1.5- to 8-times as large as a largest outer diameter of the rotormagnet.
 2. An electric motor according to claim 1, wherein the motor isa permanent magnet synchronous motor.
 3. An electric motor according toclaim 1, wherein the rotor magnet has at least one of a remanence >0.8Teslas and a high energy density >100 kJ/m³.
 4. An electric motoraccording to claim 1, wherein the rotor magnet consists of rare earthmaterials.
 5. An electric motor according to claim 1, wherein the rotormagnet consists of one of NdFeB abd SmCo.
 6. An electric motor accordingto claim 1, wherein the rotor magnet is surrounded by an sheathing. 7.An electric motor according to claim 6, wherein the sheathing of therotor magnet has a cylinder-shaped manner.
 8. An electric motoraccording to claim 1, wherein the stator is a part of an inner wall of asurrounding housing.
 9. An electric motor according to claim 1, whereinthe stator is applied as an insert into a corresponding opening of asurrounding housing.
 10. An electric motor according to claim 1, whereinthe media passage opening is free of struts between the rotor and thestator.
 11. An electric motor according to claim 1, wherein the statorhas a substantially hollow-cylindrical shape.
 12. An electric motoraccording to claim 1, wherein the rotor magnet is prepared forintegration into a shaft for integration onto a common shaft with one ofa media impeller and a media conveyor worm.
 13. An electric motoraccording to claim 1, wherein the rotor magnet is partially integratedinto one of a media impeller and a media conveyor worm.
 14. An electricmotor according to claim 1, wherein the rotor magnet is completelyintegrated into one of a media impeller and a media conveyor worm. 15.An electric motor according to claim 13, wherein one of the mediaimpeller and the media conveyor worm is composed of a material which isone of magnetically non-conductive and poorly conductive.
 16. Anelectric motor according to claim 13, wherein one of the media impellerand the media conveyor worm is composed of one of a reinforced plasticand a non-reinforced plastic.
 17. An electric motor according to claim1, wherein the stator is provided with a shielding towards an inside.18. An electric motor according to claim 17, wherein the shielding has aform of one of a tube and a flexible tubing.
 19. An electric motoraccording to claim 17, wherein the shielding is composed of electricallyand magnetically non-conductive material.
 20. An electric motoraccording to claim 1, wherein the rotor comprises a rotor shaft, therotor shaft being mounted in one of a simple manner and a multiplemanner over its length.
 21. An electric motor according to claim 20,wherein the rotor shaft is substantially mounted on one side andessentially freely projects on the other side.
 22. An electric motoraccording to claim 20, wherein at least one of the rotor and the rotormagnet are integrated into a shaft to be driven by the electric motor.23. An electric motor according to claim 20, wherein the rotor shaft ismounted in one of a non-lubricated manner and a lubricated manner bydelivery medium.
 24. An electric motor according to claim 1, wherein anaxial centre of the stator and an axial centre of the rotor aredisplaced in an axial.
 25. An electric motor according to claim 1,wherein an axial centre of the stator and an axial centre of the rotorare displaced in an axial direction by one tenth up to one fifth of alargest axial extension of the rotor magnet
 26. An electric motor foruse in an electrically aided turbocharger with a freely projectingelectric motor, for a transport of explosive gases, dusts, vapours,sticking substances, pastes, liquids; decomposing products, inventilation devices, in general pumps, in pumps for aggressive media; indisinfectable or sterilisable pumps, canned pumps, metering pumps,micro-pumps disposable pumps, multi-stage pump systems; for use inturbines, generators, conveyor worms, in devices for measuring a mediaflow via a generator voltage, the motor comprising: a stator; a rotorincluding a rotor magnet; and a media throughput opening between thestator and the rotor, wherein a smallest inner diameter of the stator is1.5- to 8-times as large as a largest outer diameter of the rotormagnet.